The invention relates generally to building control systems, and more particularly to networkable power controllers used to control electrical or electro-mechanical systems in buildings.
A building control system generally allows a building operator to control a building system within one or more buildings, such as an HVAC system (heating, ventilation, and air conditioning system), a lighting system, a water and waste system, or a security system. For example, a building control system may include a centralized or remote building control station from which a building operator may configure thermostat setting schedules and monitor temperatures in various building zones. In this manner, a building operator can manage energy use and tenant comfort in accordance with the anticipated building usage during various hours of the day.
In addition, an open systems standard for building control system networks, called BACnet, has become an important standard in the building control industry. BACnet is a data communication protocol for building automation and control networks. Using BACnet, a building operator can control and monitor building-related devices distributed throughout a network in a building. Such BACnet-compliant device may include without limitation furnaces, air conditioning systems, cooling towers, heat exchangers, lighting systems, dampers, actuators, sensors, security cameras, and other building-related devices.
Modern building control systems, however, do not commonly accommodate personal overrides of the centrally controlled settings. As such, an employee working on a weekend may be left without adequate air conditioning on a hot summer day. Typically, the employee must contact a building operator at the central control station to change the temperature setting for his or her office. In addition, even with the cooperation of the central control station, many building control systems lack the precision to override the scheduled temperature settings on merely an individual office basis. Instead, the temperature setting of an entire zone or floor of the building is temporarily modified to accommodate the single employee""s needs. Such imprecision diminishes the energy saving effect of the scheduled thermostat settings.
Individualized control of lighting systems and other building systems is also desirable, although not adequately addressed by existing solutions. For example, a building operator may schedule lighting on a floor in a building to be turned off (or turned down in intensity) after normal office hours to save energy. Without individual override control, an employee working late may be left in the dark and be unable to continue working without contacting the building operator to turn the lights back on.
Furthermore, it is not uncommon for large energy consumers, such as a grocery store operator, to negotiate for lower rates from a utility company in exchange for shedding its energy at the utility""s request. That is, if the building operator is willing to reduce its energy consumption at the request of the utility during peak demand periods (e.g., a hot summer day), the utility will charge the building operator lower overall rates for its energy consumption. For example, at a utility""s request, a grocery store may reduce the light intensity in the store gradually over a period of time. Patrons and employees tend to automatically acclimate to the slowly decreasing light intensity, without being aware of the change.
However, a conventional method for achieving such a demand reduction involves a store manager going from light switch to light switch, incrementally reducing the light intensity of various lights and/or lighting zones until the lighting throughout the store has been reduced to the appropriate level. After the demand shedding period is over, the store manager typically repeats this time-consuming process in reverse, gradually increasing the light intensity to its normal level.
In addition, existing lighting control systems typically entail considerable costs and provide, limited flexibility in configuring and powering a control network. A problem exists in providing an inexpensive network of lighting subsystems that can be installed easily throughout a building and powered conveniently by an available energy source, while providing flexible control from a central or remote control station with the convenience of individual overrides.
The above and other problems are solved by a networkable power controller that can conduct control signals for controlling an electrical device, such as a ballast of a lighting device, a BACnet device, etc. The networkable power controller can include multiple inputs, an output, and a mode selector that selects a control signal received at one of the inputs to be conducted to the output. The inputs and the output support the same signaling protocols so that multiple power controllers may be coupled together to form a network. That is, the output signal of one power controller, which is configured in accordance with the input signals and the mode selector, may be used as an input signal of a subsequent power controller. The output control signal can be used to control the power provided to or by a building automation control device in a building, including a lighting ballast or a BACnet device. Alternatively, the output control signal may control the operation of the building automation control device without directly controlling the power provided to or by the device, such as by including an analog or digital signal that causes the device to internally alter building automation control device""s consumption or generation of power.
In addition, a power controller may be powered by power received from one or more ballasts coupled to its output. In one embodiment, the power is derived from a winding in the power factor circuit of the ballast and passed into the lighting controller through its output port. A power bus in the power controller transfers the power, received at the controller""s output port, to a preceding device, such as a rotary light dimmer control, a demand load shedder, or another lighting controller.
In one aspect of the present invention, a lighting controller, which is an example of a power controller, that controls at least one ballast driving a lighting device is provided. An output signal line of the lighting controller is adapted to output an output signal satisfying a signaling protocol. The signaling protocol defining a signal format for driving the ballast. A first input signal line is adapted to receive a first input signal satisfying the signaling protocol. A second input signal line is adapted to receive a second input signal satisfying the signaling protocol. A mode selector selects among a plurality of modes, each mode determining which of the first input signal and the second input signal are conducted to the output signal line.
In another aspect of the present invention, a method for networking a power controller that controls at least one ballast driving a lighting device is provided, The power controller includes an output signal line adapted to output an output signal, a first input signal line adapted to receive a first input signal, and a second input signal line adapted to receive a second input signal. The output signal, the first input signal, and the second input signal satisfy the same signaling protocol. An output of an additional power controller is coupled to the first input signal line of the power controller. A user controllable voltage selector is coupled to the second input signal line of the power controller. A given mode is selected from among a plurality of modes. Each mode determines which of the first input signal and the second input signal are conducted to the output signal line.